Electric direction finder



KENICHI MIYA ETAL 2,955,285

ELECTRIC DIRECTION FINDER Oct. 4, 1960 Filed May 2, 1956 5 Sheets-Sheet l t i Q H f I Q Q S Q Q N i E If 31 Q 8| J3 (5 o b} J L I F;

Oct. 4, 1960 KENICHI MIYA ETAL 2,955,285

ELECTRIC DIRECTION FINDER Filed May 2, 1956 5 Sheets-Sheet 2 w i Q Oct. 4, 1960 KENICHI MIYA ETAL 2,955,285

ELECTRIC DIRECTION FINDER 5 Sheets-Sheet 3 Filed May 2, 1956 Oct. 4, 1960 KENICHI MlYA ETAL 2,955,285

ELECTRIC DIRECTION FINDER 5 Sheets-Sheet 4 Filed May 2, 1956 .Znv mars 11TH 62/ T. GaiZaki fiffai'ssewja via Oct. 4, 1960 KENICHI MIYA ETAL 2,955,285

ELECTRIC DIRECTION FINDER 5 Sheets-Sheet 5 Filed May 2, 1956 .Zrz/pezztofi6 Mb T. 5

ELECTRIC DIRECTION FINDER Kenichi Miya, Tetsuo Sasaki, and Suekichi Matsushita, Tokyo-to, Japan, assignors to Kokusai Denshin Denwa Kabushiki Kaisha, Tokyo-to, llapan- Filed May 2, 1956, Ser. No. 582,141

Claims priority, application Japan May 9, 1955 11 Claims. (Cl. 343-121) This invention relates toa direction finder, and more particularly to a direction finder capable of developing a visual indication of the direction of an intercepted electromagnetic wave signal.

An object of the instant invention is the advancement, generally, of the art of radio direction finding.

Another object of the present invention is to provide a directly visual type direction finder characterized by a high sensitivity and degree of accuracy.

Said objects and other objects have been attained by a direction finder comprising a receiving section which produces a time-division signal composed of four output voltages having divers phase relations relative to one another, said output voltages resulting from a combination of two pairs of aerials which are physically arranged on lines perpendicular to each other; an amplifier which amplifies the time-division signal; a switching device which separates the signal into direct current voltages each having a value equal to the peak value of each of said output voltages; a device which combines the direct current voltages into two pairs of output voltages capable of giving direction indication; a device which produces two alternating current voltages, each being proportional to the difference between the amplitudes of each pair of combined direct current voltages; a device which applies the alternating current voltages to the horizontal and vertical deflection plates of a cathode ray tube after amplification thereof; a device which applies a voltage having a frequency equal to that of the alternating current voltage to the intensity grid of the cathode ray tube thereby to obtain a trace of a unidirectional indication.

An ordinary electric direction finder of direct visual system heretofore in use has a low sensitivity, because of adoption of the minimum sensitivity method. Furthermore, the direction finder of time-division system heretofore in use is variant and unstable in its direction indication and is apt to be accompanied with error due to fading of the incoming signal, etc.

The direction finder in the present invention, contrary to the aforesaid defects of the direction finder heretofore in use, works with very high sensitivity and stability because peak values of time division signals are stored in the time constant circuits and the noise eifect is cancelled. Furthermore, the present invention has a characteristic that reading of direction is made easy and correct, because indication of direction is established so as to be acute.

The novel features of the present invention are set forth with particularity in the appended claims. The invention, however, both as to its manner of construction and operation together with further objects and advantages, may be best understood by reference to the following detailed description taken in connection with the accompanying drawings, in which the same elements are indicated by the same reference characters throughout the several views, and in which:

Fig. 1 is an electric connection diagram illustrating one embodiment of the basic principle of the present invention.

Fig. 2 is a diagram showing the figure on the fluorescent surface of the cathode-ray tube illustrating the basic principle of the present invention.

Figs. 3(a), 3(b), 3(c), 3(d) and 3(2), respectively, show the voltage wave forms illustrating the basic principle of the present invention.

Figs. 4, 5, and 6, are electric connection diagrams illustrating the other embodiments of the present invention.

Figs- (1) and respectively, show the voltage wave forms illustrating the basic principle of the illustration in Fig. 6.

Fig. 8 is a diagramof a converter to obtain rectangular wave, which is used in Fig. 6.

Fig. 9 is a diagram showing the figure on the fluorescent surface of a cathode-ray tube in Fig. 6.

Referring now to Fig. 1, let it be supposed that A A B and B are aerials arranged on the apexes of a regular square as in the arrangement of the Well known Adcock aerials. If a radio wave signal comes from the direction which makes an angle of B with A A then the respective outputs of the aerials A A B and B will be:

E132: E06 S111 5 wherein d is the distance between the two aerials of a pair which are confronting each other and A is the wave length of the impinging radio wave signal. As a practical matter the several voltages are developed across impedances in the aerial connecting wires in the usual manner known in the art. If the outputs of each pair of aerials are, respectively, combined differentially by transformers T and T then a combined voltage having a directivity of Figure 8 will be obtained on each secondary winding of said transformers.

EAD EA1"E g=j2E0 sin COS E oc EA2- EM: 12E0 sin cos 2 30 31- EB2=j2Eg sin sin 6) EBD EB,- E j2E sin sin ,3)

These combined voltages are successively supplied to the amplifier A through one of the exchange devices S S S and S of a switching device S per every one quarter period by switching said exchange devices in the sequence of S S S and S said device S being controlled by the output of a four-phase generator O On the other hand, theresultant voltage E at a terminal of the grounded coil inserted in the circuit of four aerials will be as follows:

Es Ear EA2+ EB1+ 132 =2E' {cos cos B)+cos Sin 5)} and it has a phase difference of with E and E This resultant voltage E is supplied to a transformer T,

and then converted to a voltage having the same phase as the phases of the voltages E and E by shifting the phase by 90 by a phase shifter I This phase shifted voltage issuperimposed on each combined voltage and is supplied to the amplifier A The same result will be obtained by another system, in Whichthe same radio Wave is received by another aerial and the output of said aerial is amplified after being properly shifted to have the same phase-as the phases of the voltages E and B and then applied to amplifier A Then, four kinds of the following voltages employed for determining the hearing are successively impressed on the amplifier A for every one quarter period of the controlling voltage of the generator 0 The output of the amplifier A is separated into voltages E Em, E and E which are, respectively, proportional to E E E and E by means of a switching device Sa the operation of which is controlled by the output of the four phase generator O as in the case of the switching device S. 1 V v The voltages E E E and E; are, respectively, supplied to the peak value rectifier circuits D D D and D through one of the exchange devices S S S and S of a switching device Sa by sequential switching in the order of S S g, S and S whereby the direct current voltages proportional to the separated alternating current voltages E E E and E; are taken out of the rectifier circuits D D D and D The direct current voltages taken vout as hereinbefore described are combined in two pairs and then are, respectively, supplied to the converters F and F of the indicating device, to convert their waves into such sine waves as shown in Fig. 2(b) and Fig. 2(d), which are, respectively, proportional to the difference between the voltages E and E and between E and E The output voltages of converters F and F are respectively made'as the northsouth and east-west components and these components are supplied to the vertical and horizontal deflection circuits of a cathode-ray tube B to'indicate a linear figure on the fluorescent surface. On the other hand, a voltage, which is produced by properly shifting a part of the output of the generator 0 by a phase shifterrb, and by tained.

Furthermore, in case I RI l ADl l Rl I BDl the indication angle 0 becomes the value shown in the following Formula 8, without relation to the magnitude of E whereby the direction corresponding to ,8 can be indicated. v

#5 j2E =sin cos 8) Moreover, if sc' uare law detectors are used as rectifier circuits D ,-D D and D itwill become as follows:

".7 n aD .1 a Ap-- If only the condition E O is satisfied, the angle 0 may be more approximated to ,8 even if the condition in Formula 7 is not satisfied. Moreover, when square law amplification characteristic is given to an amplifier A91, instead of employing square law detectors as the circuits D D D and D the same result will be obteat-' ,s 9

The hereinbefore disclosed system relates to the case, in which Adcock aerials are used but a linearfigure such as described above can also be obtained by using loop aerials and a vertical aerial which are located at right angles to each other.

As a means for combining the outputs of four aerials, besides the above-mentioned method, the-following method may be used. Namely, referring to Fig. 4, aerials 3 A A B and B are arranged in the same way as Fig. l.

rectifying said shifted voltage through the rectifier D the wave of said voltage being shown by the full line of Fig. 2(e), is supplied to the intensity control grid of the cathode-ray tube B to make the half period of the linear figure blank thereby to obtain an unidirectional indication of the bearing of the radio wave as shown in Fig. 3.

7 of the voltage E the phase of said component being same with the phase of the voltage E (or B is E and the other component of said voltage E the phase of said component being orthogonal to the former com ponent, is E then E is expressed by the following formula.

The output voltages H E Em and E of said aerials are, respectively, shown in Formula 1. If the phases of said output voltages are shifted by a phase shifter P; by a certain angle take sin [3,

'. When the voltages whose phases are shifted and thevoltages having shifted phases and the voltages having unshifted phases are combined differentially, the following combined outputs for determining the direction are obtained at points a a b and b; by using Formulas l 1 and 10.

When a linear detector is employed as the rectifier circuits D D D and D the following indication angle 0 of a cathode-ray tube B is obtained by substituting the Formula 5 for Formula 4.

0 tan- 7 output of 0 Then, these time division signals are,

52 U after being amplified by a common amplifier Apr, selected in the order of al, E B and E by a switching circuit Sa as described in case of Fig. l, and then rectified by peak value rectifier circuits D D D and D These rectified voltages are successively supplied to the alternating current converters F and F to obtain sine wave voltages which are, respectively, proportional to the difierence between the voltages E and E and between the voltages E and E These sine waves are, respectively, supplied to the vertical and horizontal deflection circuits of the cathode-ray tube B as the southnorth and east-west components. Then, the indication angle of the cathode-ray tube B will be given by the following Formula 12.

Said angle indicates the bearing of the radio wave.

Fig. 5 shows a connection diagram (abridged partly) of one embodiment of the switching device S11 in Figs. 1 and 4. The output voltages which are received by the aerials A A B and B and then combined, and converted into time-division outputs at the receiving section R by an electric switching device (not shown) controlled by the generator 0 The combined outputs obtained alternately from these outputs are supplied to the indication section Y and to the indication section X, and detailed explanation will be made hereunder. Since the sections Y and X are structurally and operationally equivalent, only the indication section Y will be completely described.

The time-division signals are supplied to the rectifier tubes V and V through the condensers C and C The tubes V and V are so controlled by applying the output voltage of the generator 0 to the grids of said tubes through a phase shifter I capable of properly shifting the phase of said output voltage and a transformer T and by properly selecting the bias voltage E that the tube V is rendered conductive only when the voltage E is arriving and the tube V is rendered conductive only when the voltage E is arriving. Accordingly, an electric current proportional to the value of B flows through the tube V only when the voltage E is arriving and charges the condenser C which constitutes a time constant circuit with R. If the time constant CR is made suificiently large, the charged voltage which is proportional to the peak value of the voltage E is kept constant until the next voltage E arrives, and is supplied to the suppressor grid of the modulation tube V as a negative direct current voltage. The same applies also to the tube V so that said tube supplies a negative direot current voltage which is proportional to the value of E to the suppressor grid of the modulation tube V On the other hand, the alternating current voltage of the generator 0 is supplied to the control grids of the vacuum tubes V and V through a transformer T Accordingly, the voltages c and e the amplitudes of which are, respectively, proportional to the voltages E and E as shown in Fig. 2(a) are generated at the plates of said tubes. These voltages are combined differentially by the transformer T to obtain an alternating current voltage such as shown in Fig. 2(b) by E,,, said last-mentioned voltage being supplied to the vertical deflection circuit of the cathode-ray tube B.

Concurrently, in the amplifier device X, the voltages shown by e and e in Fig. 2(a) which are proportional to the value of the voltages E and Ebg are obtained and differentially combined to obtain the alternating current voltages as shown by E, in Fig. 2(d) in the same Way as described in connection with the voltage supplied to the vertical deflection circuit of the cathode ray oscilloscope, said voltage being supplied to the horizontal deflection circuit of said tube B. Accordingly, such a linear 0=tan figure having an angle 6 to the axis Y at the original point 0 as shown in Fig. 3 will be indicated on the fluorescent surface of the cathode-ray tube B. Moreover, the output of the generator 0 is properly shifted in its phase by a phase shifter Q rectified by a rectifier tube V and then supplied to the intensity control grid of tube B as a negative voltage for half a period. Consequently, the part of the trace shown by broken line of the linear figure in Fig. 3 is blanked, whereby the bearing of the radio wave is shown by an unidirectional indication. In the above case, for the purpose of obtaining a linear figure on the cathode-ray tube, the alternating current voltages to be supplied to the tubes V V and V do not necessarily need the output of the generator 0 for switching device and any other alternating current power source may well be used.

As above-mentioned, rectification of a peak value by using a circuit having a large time constant has advantages that the indication of direction is very stable and the bearing of radio wave is correctly indicated even when the radio Wave having the same or more communication speed as compared with the switching speed of the above-mentioned direction finder of time division system is to be measured or when the radio wave followed by a rapid fading is to be measured. Moreover, as the set noise contained in the four time-division signals is of the same value, the noise is nearly cancelled by taking the difference between the voltages of each of the pairs after rectification of the peak value. Therefore, a correct direction indication of a radio wave can be obtained by reason of the substantial reduction in the magnitude of the signal-to-noise ratio.

Fig. 6 shows a modification of the system shown in Fig. 5. By this system, in the same manner as the case of Fig. 5, direct current voltages -e and e, proportional to the voltages E and B are obtained from the peak value rectification circuit having the time constant CR. However, in the embodiment in Fig. 6 there is a characteristic in the manner to be used for indicating difference between said voltages on the cathode-ray tube. Namely, the voltages c and e are changed over alternately as shown in Fig. 7(a), by a switching device S, such as a vibrator which works by the output of the generator O and then are supplied to the control grid of a vacuum tube V (Instead of a vibrator, other switching devices, vacuum tubes and etc. may well be used.) The operating range of tube V is regulated so that only the linear part of the characteristic E,;I of said tube may be employed as shown in Fig. 8. When said voltages e,. and e which are changed over alternately as in case of Fig. 7(a), are supplied to the control grid of the tube V a rectangular output wave voltage is de veloped like in Fig. 7( b), said wave having an amplitude e,,=K'(]e,, ][e [)=K(!E l--]E and proportional to the difference between the absolute values of said voltages. A condenser C is used to suppress the transient phenomenon in the moving period of the tongue of the vibrator 8,.

Then, the rectangular output wave is supplied to a differential circuit which is composed of a condenser C and a resistance R the time constant of which circuit being sufficiently small as compared with the half a period of said rectangular wave. At the two terminals of the resistance R a voltage, having the amplitude Ze and attenuating exponentially from the maximum value as shown in Fig. 7(c) is obtained. This differentiated voltage is amplified to a proper value by an amplifier A of a high fidelity, and then is supplied to the vertical deflection circuit of a cathode-ray tube B. Concurrently, at the indication section X, a differentiated voltage is supplied to the horizontal deflection circuit of said tube B by the same process as mentioned above.

That is to say, a rectangular wave voltage having an amplitude e as shown in Fig. 7(e), said amplitude being proportional to the difference between the absolute Values of such voltages e and e as shown in Fig. 7 (d), is obtained [from the voltage obtained by changing alternately the direct current voltages e-,, and e which are, respectively, proportional to the voltagesE and E Said rectangular wave voltage is so differentiated as to become the volt-age having a wave form as shown in Fig. 7(f), which is amplified by an amplifier of a high fidelity. This amplified voltage is supplied to the horizontal deflection curcuit of said tube B. Consequently, on the fluorescent surface of said tube B a linear trace is developed which is thick at its original point and is becoming thinner towards its extremity. The angle inclination of said linear figure is determined by tan" (e /e,,) v

As is clear from the wave forms of the voltages supplied to the cathode-ray tube, the attenuation is rapid at the peaked wave part and slow at the basic portion, so that a substantially long time is required until the wave approaches zero, so that the figure on the cathoderay tube is thin at the end and thick near the original point. Then, when such a blanking voltage as shown in Fig. 7(g) is supplied to the cathode-ray tube, the portion of the trace indicated in broken line of Fig. 9 is blanked and the direction of the incoming radio wave signal can be indicated clearly and unidirectionally similarly to the indication of a compass needle. Moreover, for the production of alternating current voltage to be supplied to the switching device S and to the blanking device T, the output of the generator is indispensable, and other alternating current power source such as a commercial power source may be utilized.

While we have described and shown particular embodiments of our invention, it will, of course, be understood that we do not wish to be limited thereto, since many modificationsmay be made and we, therefore, contemplate by the appended claims to' cover all such modifications as fall within the true spirit and scope of our invention.

What is claimed is:

l. A direct-ion finder comprising an antennasystem including four independent aerials each of which is positioned at the apex of a square and adapted to concurrently derive a potential signal having a phase correlative to the bearing of an incoming radio wave relative to the respective aerial, circuit means for difierentially combining the potential signals derived by each pair of diagonally positioned aer-ials, circuit means tor developing a resultant signal corresponding to the sum of all of said potential signals and for superimposing said resultant signal upon each of said differentially combined potential signals, circuit means for sequentially amplifying and separating ea'chof said diiferentially combined potential signals subsequent to superimposition of said resultant signal thereon at a predetermined rate, circuit means for developing direct current voltages each of which is proportional to the peak value of one of said amplified and separated potential signals, circuit means for producing a pairof sinusoidal signals, each of which is proportional to the difference between two of said direct current voltages, a cathode ray oscilloscope, circuit means for .individually impressing said pair of sinusoidal signals upon the horizontal and vertical deflection plates of said cathode ray oscilloscope thereby developing a linear trace on the screen thereof, and circuit means for impressing uponthe intensity control grid of said cathode ray oscilloscope a pulsating unidirectional signal having a period correlative to said predetermined rate thereby to selectively blank a portion of said linear-trace on said screen.

2. A direction finder comprising anantenna system including four independent aerials each of which is physically positioned at the apex of a square and adapted ,to simultaneously derive a potential signal havinga phase correlative to the bearing'of an incoming electromagnetic wave relative to the respective aerial, transformer means coupled across the diagonal ones of said :a ials, tor de- 8 veloping differential signals proportional to the potential signals derived by said aerials, amplification circuit means for developing amplified output signals, first switching circuit means coupled to said transformer means for effecting sequential application of said diiferential signals. to said amplification circuit means, transformer means coupled to said antenna system for producing a resultant signal corresponding to the sum of all of said derived potential signals, circuit means for selectively shifting the phase of-said resultant signal, circuit means for impressing said resultant signal upon each of said dilferential signals immediately prior to amplification thereof by said amplification circuit means, second switching circuit means coupled to said amplification circuit means for effecting sequential separation of said amplified out put signals, detector circuit meansindividm ally coupled to each of said second switching circuit means for developing unidirectional current signals correlative to the respective separated amplified output signals, a pair of converter circuit means each being indi vidually coupled to a unique pair of said detector circuit means for producing a pair of sinusoidal signals each of which is proportional to the difference between the unidirectional current signals developed by said unique pair of detector circuits, a cathode ray oscilloscope, circuit means for individually impressing each of said pair of sinusoidal signals upon the horizontal and vertical deflection circuits of said cathode ray oscilloscope, and there- ,by develop :a linear trace on the screen thereof, and circuit means tor impressing upon the intensity control grid of said cathode ray oscilloscope a unidirectional signal for effecting blanking of a portion of said linear trace.

3. In a direction finder according to claim 2 wherein each of said detector circuit means is a linear detector.

4. In a direction finder according to claim 2 wherein each of said detector circuit means is a square law detector.

5. In a direction finder according to claim 2, and including circuit means for effecting synchronous sequential operation of said first and second switching circuit means.

6. In a direction finder-according to claim 5 wherein said circuit means comprises a four phase alternating current generator. 7 i

7. A circuit for developing an output alternating current signal correlative to the sum of a pair'of sequential alternating current input signals comprising an input terminal to which the pair of signals are applied, a pair of capacitors, a common terminal, a pair of triodes the respective cathodes of which are connected to said common terminal and the respective plates of which are individually coupled to said input terminal through one of said capacitors, a first transformer the secondary winding of which is connected between the respective control grids of said triodes, a first fixed bias source interposed between said common terminal and the center of said secondary winding, a phase shifter, an alternating current source coupled to the primary winding of said transformer through said phase shifter for varying the bias on said triodes at a rate whereby one of said triodes conducts upon the application of one of the input signals and the other of said'triodes conducts upon the application' of the other of the input signals, a pair of energy storage networks individually coupled between the plates of each of said triodes and said common terminal, each of said networks being chargeable'to an energy level corresponding to the peak valueof the input signal to which its associated triode is rendered conductive, a second fixed bias source having one terminal connected to said common terminal, a second transformer the primary winding of which is connected between said common terminal and said source, a pair of pentodes the respective cathodes of which are connected to said common terminal and the respective control grids of which are connected to one end of the primary winding of said second transformer, the other end of the primary winding being connected to the other terminal of said second source, the respective suppressor grids being individually coupled to one of said energy storage networks, and an output transformer connected between the plates of said pentodes for differentially combining the signals developed on the plates of said pentodes in response to the energy in said networks.

8. A circuit for developing an output signal correlative to the sum of a pair of sequential alternating current input signals comprising an input terminal to which the pair of input signals are applied, a common terminal, a pair of capacitors, a pair of triodes the respective cathodes of which are connected to said common terminal 'and the respective plates of which are individually coupled through one of said capacitors to said input terminal, a transformer the secondary winding of which is connected between the respective control grids of said triodes, a fixed bias source interposed between said common terminal and the center of said secondary winding, a phase shifter, an alternating current source coupled to the primary Winding of said transformer through said phase shifter for varying the bias on said triodes at a rate whereby one of said triodes conducts only upon the application of one of the input signals and the other of said triodes conducts only upon the application of the other of the input signals, a pair of energy storage networks individually coupled between the plates of each of said triodes and said common terminal, each of said networks being chargeable to an energy level corresponding to the peak value of the input signal to which its associated triode is rendered conductive, a linearly operated electron tube, a circuit switching device alternately interconnecting said electron tube to one of said networks at a rate controlled by said alternating current source for impressing upon the control grid of said electron tube rectangular pulses correlative to the charge on said networks, said electron tube thereby developing an output rectangular pulse having an amplitude proportional to the difference between the absolute values of the pulses applied thereto, a differentiating network connected to said electron tube for selectively differentiating the output rectangular pulses thereof, said difierentiating network having a time constant characteristic small compared with the half period of said output rectangular pulse, and circuit means for amplifying the difierentiated pulses.

9. A circuit according to claim 8 wherein said circuit switching device comprises a vibrator.

10. A circuit according to claim 9 and including a condenser connected across said vibrator for suppressing certain transient phenomenon therein.

11. A direction finder comprising an antenna system including four independent aerials each of which is physically positioned at the apex of a square and adapted to simultaneously derive a potential signal having a phase correlative to the bearing of an incoming electromagnetic wave relative to the respective aerial, circuit means for developing two output signals each of which results from the differential combination of the potential signals derived by each pair of diagonally positioned aerials, circuit means for developing a resultant signal corresponding to the sum of all of said derived potential signals and for superimposing said resultant signal upon each of said two output signals, circuit means for sequentially amplifying and separating each of said two output signals subsequent to the superimposition of said resultant signal thereon at a predetermined sequential rate, circuit means for developing a pair of individual unidirectional signals each of which is proportional to the peak value of a respective one of said two output signals, circuit means individual to each of said last recited circuit means for developing rectangular pulses having an amplitude proportional to the difference between the absolute values of successive signals in each of said pair of unidirectional signals, circuit means individual to each of said last recited circuit means for developing a differentiated signal from each of the developed rectangular pulses, a cathode ray oscilloscope, circuit means individually intercoupliug the horizontal and vertical deflection circuits of said oscilloscope to one of said last recited circuit means for applying the differentiated signal to said deflection circuits thereby to develop a linear trace on the screen thereof, said trace having a gradually decreasing thickness, and circuit means for impressing upon the intensity control grid of said oscilloscope a unidirectional rectangular pulse for blanking a portion of said linear trace.

References Cited in the file of this patent UNITED STATES PATENTS 2,408,039 Busignies Sept. 24, 1946 2,456,666 Agate Dec. 21, 1948 2,476,977 Hansel July 26, 1949 2,485,642 Newitt Oct. 25, 1949 

